Cement dispersant, method for producing polycarboxylic acid for cement dispersant and cement composition

ABSTRACT

The present invention provides a method for producing a cement dispersant having high percentage in water reduction-rate and appropriate air-entraining property. This method for producing a polycarboxylic acid for a cement dispersant is characterized in that alkylene oxide is added at a specific temperature range.

BACKGROUND OF THE INVENTION

A. Technical Field

The present invention relates to a cement dispersant, a method forproducing a polycarboxylic acid for a cement dispersant and a cementcomposition. More specifically, it relates to a cement dispersantsynthesized by using a polyalkylene glycol ester type monomer or apolyalkylene glycol-ether type monomer, having alkylene oxide obtainedby the addition reaction in a specific temperature range, and a cementdispersant which can achieve high percentage in water reduction, amethod for producing a polycarboxylic acid for such a cement dispersantand a cement composition.

B. Background Art

In recent concrete fields, improvement in durability and strength ofconcrete structures is strongly demanded. Reduction in unit water amountis an important subject, and development of high performance AE waterreducing agents is energetically conducted in each cement admixturemaker. Of those, polycarboxylic acid type high performance AE waterreducing agents have the excellent characteristic which exhibitsextremely high water reducing property which cannot be achieved by otherhigh performance AE water reducing agents such as naphthalene type.However, the water reducing performance is not still sufficient.

SUMMARY OF THE INVENTION

A. Objects of the Invention

An object of the present invention is to provide a cement dispersantwhich improves water reducing performance, a method for producing acement dispersant and a cement composition.

B. Disclosure of the Invention

The present inventors have found that a polycarboxylic acid for a cementdispersion, obtained by a specific production method is an excellentcement dispersion exhibiting high water reducing performance, and havecompleted the present invention. That is, the present invention is toprovide a cement dispersant exhibiting high water reducing performance,a method for producing a polycarboxylic acid for a cement dispersant anda cement composition.

The above various objects are achieved by

(1) a cement dispersant containing a polycarboxylic acid having apolyalkylene glycol at a side chain, wherein the polyalkylene glycol isobtained by adding alkylene oxide in a range of 80 to 155° C.

The present invention is also achieved by

(2) a cement dispersant comprising a polycarboxylic acid having apolyalkylene glycol at a side chain, wherein the polycarboxylic acidcomprises a polyalkylene glycol type monomer unit having a polyalkyleneglycol at a side chain and a carboxylic acid type monomer unit,characterized in that, as a polyalkylene glycol type monomer giving thepolyalkylene glycol type monomer unit, a polyalkylene glycol typemonomer having a molecular weight distribution which has a main peak,but has no second peak on the higher molecular weight side of the mainpeak, or has a second peak on the higher molecular weight side of themain peak-in an area ratio of 8% or less based on the total area of themain peak and the second peak.

The present invention is also achieved by

(3) a method for producing a polycarboxylic acid for a cementdispersant, having a polyalkylene glycol at a side chain, characterizedby adding alkylene oxide to an active hydrogen-containing compound in arange of 80 to 155° C.

Further, the present invention is achieved by

(4) a method for producing a polycarboxylic acid for a cement dispersantcomprising, as repeating units, a polyalkylene glycol ether type unit(I) represented by the general formula (1)

(where, R¹ to R³ each independently represent hydrogen or methyl group,R⁵O represents one kind or a mixture of two or more kinds of oxyalkylenegroup having 2 to 4 carbon atoms, in the case of two or more kinds,those may be added in a block state or random state, R⁶ representshydrogen, alkyl group having 1 to 22 carbon atoms, phenyl group, oralkyl phenyl group (the alkyl group in the alkyl phenyl group having 1to 22 carbon atoms), R⁴ represents —CH₂—, —(CH₂)₂— or —C(CH₃)₂—, and prepresents an integer of 1 to 300), and a dicarboxylic acid type unit(II) represented by the general formula (2)

(where, M¹ and M² each independently represent hydrogen, monovalentmetal, divalent metal, ammonium or organic amine, X represents —OM², or—Y—(R⁷O)rR⁸, Y represents —O—, or —NH—, R⁷O represents one kind or amixture of two or more kinds of oxyalkylene group having 2 to 4 carbonatoms, in the case of two or more kinds, those may be added in a blockstate or a random state, R⁸ represents hydrogen, alkyl group having 1 to22 carbon atoms, phenyl group, aminoalkyl group, alkyl phenyl group, orhydroxyalkyl group (each alkyl group in the aminoalkyl, alkyl phenyl andhydroxyalkyl groups having 1 to 22 carbon atoms), r is an integer of 0to 300, and an acid anhydride group (—CO—O—CO—) may be formed in placeof the —COOM¹ and COX groups between carbon atoms to which the —COOM¹and COX groups should be bonded respectively), characterized in that apolyalkylene glycol ether type monomer obtained by addition reaction ofalkylene oxide having 2 to 4 carbon atoms in a range of 80 to 155° C.with an unsaturated alcohol (B-1) represented by the general formula (3)

(where, R¹ to R³ each independently represent hydrogen, or methyl group,and R⁴ represents —CH₂—, —(CH₂)₂—, or —C(CH₃)₂—) is used as apolyalkylene glycol ether type monomer giving the general formula (1)which is the repeating unit.

Furthermore, the present invention is achieved by

(5) a method for producing a polycarboxylic acid for a cementdispersion, wherein the polycarboxylic acid comprises, as repeatingunits, a polyalkylene glycol ester type unit (III) represented by thegeneral formula (4)

(where, R⁹ represents hydrogen, or methyl group, R¹⁰O represents onekind or a mixture of two or more kinds of oxyalkylene group having 2 to4 carbon atoms, in the case of two or more kinds, those may be added ina block state or random state, R¹¹ represents alkyl group having 1 to 22carbon atoms, phenyl group, or alkyl phenyl group (the alkyl group inthe alkyl phenyl group having 1 to 22 carbon atoms), and s is an integerof 1 to 300), and a monocarboxylic acid type unit (IV) represented bythe general formula (5)

(where, R¹² represents hydrogen, or methyl group, and M³ representshydrogen, monovalent metal, divalent metal, ammonium, or organic amine),characterized in that a polyalkylene glycol (6) obtained by additionreaction of alkylene oxide having 2 to 4 carbon atoms with an alcohol(B-2) represented by the general formula (7) in a range of 80 to 155° C.is used in producing a polyalkylene glycol ester type monomer giving therepeating unit (III) by esterification between the polyalkylene glycol(6) represented by the general formula (6) and (meth)acrylic acid orester interchange between the polyalkylene glycol (6) andalkyl(meth)acrylates (the alkyl group in the alkyl(meth)acrylates having1 to 22 carbon atoms).

HO—(R¹⁰O)s—R¹¹  (6)

(where, R¹⁰O represents one kind or a mixture of two or more kinds ofoxyalkylene group having 2 to 4 carbon atoms, in the case of two ormore, those may be added in a block state or random state, R¹¹represents alkyl group having 1 to 22 carbon atoms, phenyl group, oralkyl phenyl group (the alkyl group in the alkyl phenyl group having 1to 22 carbon atoms), and s is an integer of 1 to 300)

HO—R¹¹  (7)

(where, R¹¹ represents alkyl group having 1 to 22 carbon atoms, phenylgroup, or alkyl phenyl group (the alkyl group in the alkyl phenyl grouphaving 1 to 22 carbon atoms))

Furthermore, the present invention is achieved by

(6) a method for producing a polycarboxylic acid for a cement-dispersantas shown in (3), (4) or (5) above, characterized in that the additionreaction of the alkylene oxide is conducted in the presence of a basecatalyst.

Furthermore, the present invention is achieved by

(7) a cement dispersant comprising a polycarboxylic acid for cementdispersant obtained by the method as shown in (3), (4), (5) or (6)above.

Furthermore, the present invention is achieved by

(8) a cement composition comprising at least water, a cement and acement dispersant, characterized in that as the cement dispersant thecement composition comprises the cement disperse as shown in (1), (2) or(7) above.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a GPC chart of ‘IPN-35’ as produced in Example 1.

FIG. 2 shows a GPC chart of ‘IPN-35’ as produced in Example 2.

FIG. 3 shows a GPC chart of ‘IPN-35’ as produced in Comparative Example1.

DETAILED DESCRIPTION OF THE INVENTION

As a polycarboxylic acid having a polyalkylene glycol at a side chainobtained by adding alkylene oxide to an active hydrogen containingcompound, there are exemplified a polycarboxylic acid comprising therepeating units (I) and (II) and a polycarboxylic acid comprising therepeating units (III) and (IV).

The repeating unit (I) is one shown by the above general formula (1).Examples of a monomer giving such a repeating unit are compoundsobtained by adding 1 to 300 moles of alkylene oxide to an unsaturatedalcohol, such as allyl alcohol, methallyl alcohol,3-methyl-3-butene-1-ol, 3-methyl-2-butene-1-ol, or2-methyl-3-butene-2-ol. Those are used in one kind or two or more kinds.

In order to obtain high water reducing performance, it is important todisperse cement particles with steric repulsion and hydrophilicity dueto polyalkylene glycol chain contained in the repeating units (I) and(III). For this, it is preferable that many oxyethylene groups areintroduced into the polyalkylene glycol chain. Further, it is mostpreferable to use the polyalkylene glycol chain in which an averageaddition mole number of the oxyalkylene group is 1 to 300, butpolyalkylene glycols having the average addition mole number of 1 to100, or 5 to 100 are proper from the point of polymerizability andhydrophilicity.

The repeating unit (II) is one shown by the above general formula (2).Examples of monomers giving the repeating unit (II) are maleic acid,maleic anhydride, half-ester of-maleic acid and alcohol having 1 to 22carbon atoms, half-amide of maleic acid and amine having 1 to 22 carbonatoms, half-amide or half-ester of maleic acid and amino alcohol having1 to 22 carbon atoms, half-ester of a compound (C) obtained by adding 1to 300 moles of oxyalkelene having 2 to 4 carbon atoms to those alcoholsand maleic acid, half-amide of a compound in which hydroxyl group at oneend of the compound (C) is aminated and maleic acid, half-ester ofmaleic acid and glycol having; 2 to 4 carbon atoms, or polyalkyleneglycol in which the addition mole number of those glycols is 2 to 100,half-amide of maleamic acid and glycol having 2 to 4 carbon atoms, orpolyalkylene glycol in which the addition mole number of those glycolsis 2 to 100, and their monovalent metal salts, divalent metal salts,ammonium salts, and organic amine salts, and the like. Those can be usedin one kind or two or more kinds.

The repeating unit (III) is one shown by the above general formula (4).Examples of the monomer giving the repeating unit (III) are esterifiedproducts of alkoxypolyalkylene glycol and (meth)acrylic acid, such asmethoxypolyethylene glycol mono(meth)acrylate, methoxypolypropyleneglycol mono(meth)acrylate, methoxypolyethylene glycol polypropyleneglycol mono(meth)acrylate, methoxypolybutylene glycolmono(meth)acrylate, or methoxypolyethylene glycol polybutylene glycolmono(meth)acrylate. Those can be used in one kind or two or more kinds.

In order to obtain high water reducing performance, it is important todisperse cement particles with steric repulsion and hydrophilicity dueto polyalkylene glycol chain contained in the repeating unit (III). Forthis, it is preferable that many oxyethylene groups are introduced intothe polyalkylene glycol chain. Further, it is most preferable to use thepolyalkylene glycol chain in which an average addition mole number ofthe oxyalkylene group is 1 to 300, but polyalkylene glycols having theaverage addition mole number of 1 to 100, or 5 to 100 are proper fromthe point of polymerizability and hydrophilicity.

The repeating unit (IV) is one shown by the above general formula (5).Examples of the monomer giving the repeating unit (IV) are (meth)acrylicacid, and their monovalent metal salts, divalent metal salts, ammoniumsalts, and organic amine salts. Those can be used in one kind or two ormore kinds.

If necessary, a repeating unit (V) other than the repeating units (I)and (II) can be introduced. Examples of the monomers giving therepeating unit (V) are unsaturated dicarboxylic acids, such as fumaricacid, itaconic acid, or citraconic acid, and their monovalent metalsalts, divalent metal salts, ammonium salts, and organic amine salts,and monoesters or diesters of those acids and alkyl alcohol having 1 to20 carbon atoms and-glycol having 2 to 4 carbon atoms or polyalkyleneglycol having addition mole number of their glycols of 2 to 100;diesters of maleic acid and alkyl alcohol having 1 to 20 carbon atoms orglycol having 2 to 4 carbon atoms or polyalkylene glycol having additionmole number of their glycols of 2 to 100; (meth)acrylic acid and theirmonovalent metal salts, divalent metal salts, ammonium salts, organicamine salts, and esters of those acids and alkyl alcohol having 1 to 20carbon atoms and glycol having 2 to 4 carbon atoms or polyalkyleneglycol having addition mole number of their glycols of 2 to 100;unsaturated sulfonic acids, such as sulfoethyl (meth)acrylate, 2-methylpropanesulfonic acid (meth)acylamide, or styrenesulfonic acid, and theirmonovalent metal salt, divalent metal salts, ammonium salts and organicamine salts; unsaturated amides, such as (meth)acrylamide or(meth)acrylalkyl amide; vinyl esters, such as vinyl acetate or vinylpropionate; aromatic vinyls, such as styrene; and the like. Those can beused in one kind or two or more kinds.

If necessary, a repeating unit (VI) other than the repeating units (III)and (IV) can be introduced. Examples of the monomers giving therepeating unit (VI) are unsaturated dicarboxylic acids, such as maleicacid, fumaric acid, itaconic acid, or citraconic acid, and theirmonovalent metal salts, divalent metal salts, ammonium salts, andorganic amine salts, and monoesters or diesters of those acids and alkylalcohol having 1 to 20 carbon atoms and glycol having 2 to 4 carbonatoms or polyalkylene glycol having addition mole number of theirglycols of 2 to 100; (meth)acrylic acid, and their monovalent metalsalts, divalent metal salts, ammonium salts, and organic amine salts,and esters of those acids and alkyl alcohol having 1 to 20 carbon atomsand glycol having 2 to 4 carbon atoms or polyalkylene glycol havingaddition mole number of their glycols of 2 to 100; unsaturated sulfonicacids, such as sulfoethyl (meth)acrylate, 2-methyl propanesulfonic acid(meth)acrylamide, or styrenesulfonic acid, and their monovalent metalsalt, divalent metal salts, ammonium salts and organic amine salts;unsaturated amides, such as (meth)acrylamide, or (meth)acrylalkyl amide;vinyl esters, such as vinyl acetate or vinyl propionate; aromaticvinyls, such as styrene; and the like. Those can be used in one kind ortwo or more kinds.

The monomer giving the repeating unit (I) can be produced by additionreaction of the unsaturated alcohol (B-1), which is an active hydrogencontaining compound, and the alkylene oxide having 2 to 4 carbon atoms,and the monomer giving the repeating unit (III) is obtained byesterification between the polyalkylene glycol (6) obtained by additionreaction of the alcohol (B-2), which is an active hydrogen containingcompound, and the alkylene oxide having 2 to 4 carbon atoms and(meth)acrylic acid or ester interchange between the polyalkylene glycol(6) and alkyl(meth)acrylates.

Examples of such alkyl(meth)acrylates are methyl (meth)acrylate, ethyl(meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, isopropyl(meth)acrylate, isobutyl (meth)acrylate, pentyl (meth)acrylate, hexyl(meth)acrylate, heptyl (meth)acrylate, and the like. Those can be usedin one kind or two or more kinds.

The unsaturated alcohol (B-1) is one shown by the general formula (3).Examples of the unsaturated alcohol (B-1) are unsaturated alcohols, suchas allyl alcohol, methallyl alcohol, 3-methyl-3-butene-1-ol,3-methyl-2-butene-1-ol, or 2-methyl-3-butene-2-ol. Those can be used inone kind or two or more kinds.

The polyalkylene glycol (6) is one shown by the above general formula(6). Examples thereof are methoxypolyethylene glycol,methoxypolypropylene glycol, methoxypolyethylene glycol polypropyleneglycol, methoxypolybutylene glycol, and the like. Those can be used inone kind or two or more kinds.

The alcohol (B-2) is one shown by the above general formula (7).Examples thereof are methyl alcohol, ethyl alcohol, propyl alcohol,butanol, pentanol, isobutanol, isopropanol, phenol, and the like. Thosecan be used in one kind or two or more kinds.

Examples of the alkylene oxide having 2 to 4 carbon atoms areethyleneoxide, propyleneoxide, or butyleneoxide and the like. Those canbe used in one kind or two or more kinds.

The addition temperature in addition reaction of the unsaturated alcohol(B-1) and the alkylene oxide having 2 to 4 carbon atoms and in additionreaction of the alcohol (B-2) and the alkylene oxide having 2 to 4carbon atoms must be within the range of 80 to 155° C., preferablywithin the range of 90 to 150° C., or more preferably within-the rangeof 100 to 140° C. That is, in the polycarboxylic acid of the presentinvention which comprises the repeating units (I) and (II), and in thepolycarboxylic acid of the present invention which comprises therepeating units (III) and (IV), in a copolymer obtained using a monomerobtained by addition reaction at high temperature of more than 155° C.,copolymerizability of the monomer is low, and the weight averagemolecular weight does not freely rise to the desired value. As a result,in the case of using as a cement dispersant, excessive addition amountis necessary, resulting in high cost, the water reducing performance islow, and the slump loss preventing effect is low. In contrast to this,if the temperature is lower than 80° C., addition rate is slow, andproductivity decreases. Thus, the reason that the addition reactiontemperature has the optimum range as the performance of a cementdispersant is unclear, but it is a surprising matter.

As the polyalkylene glycol type monomer (such as a polyalkylene glycolether type monomer obtained by adding the alkyleneoxide to the theunsaturated alcohol (B-1), a polyalkylene glycol ester type monomerobtained by esterification between a polyalkylene glycol and(meth)acrylic acid wherein the polyalkylene glycol obtained by additionreaction of the alkylene oxide to the alcohol (B-2), or a polyalkyleneglycol ester type monomer obtained by ester interchange between thepolyalkylene glycol and alkyl(meth)acrylates) giving such a polyalkyleneglycol ether type unit (such as the polyalkylene glycol ether type unitbeing the repeating unit (I) and the polyalkylene glycol ester type unitbeing the repeating unit (III)) of the polycarboxylic acid of thepresent invention, there can be used, for example, a monomer having amolecular weight distribution which has a main peak, but has no secondpeak on the higher molecular weight side of the main peak, or has asecond peak on the higher molecular weight side of the main peak in anarea ratio of 8% or less, preferably 6% or less, based on the total areaof the main peak and the second peak. The second peak on the highermolecular weight side of the main peak seems to be caused by, forexample, that partial polymerization occurs to form olygomers or othersubstances when adding the alkylene oxide to the active hydrogencontaining compound. As the addition temperature becomes higher, thearea ratio of the second peak on the higher molecular weight side of themain peak increases, and at last, when the addition temperature has goneover 155° C., the area ratio exceeds 8%. As a result, the molecularweight becomes difficult to increase in the copolymerization with thecarboxylic acid type monomer, so the above-mentioned disadvantageappears. Shapes of the second peak on the higher molecular weight sideof the main peak is not limited to a peak independent of the main peak,but includes those such as a peak partially overlapping with the mainpeak or a shoulder-shaped peak forming a shoulder of the main peak.

To obtain the polycarboxylic acid for a cement dispersant of the presentinvention, the above-mentioned monomers are copolymerized with apolymerization initiator. The polycarboxylic acid for a cementdispersant can be produced by conventional methods, such as solutionpolymerization or bulk polymerization.

The solution polymerization can be conducted in a batchwise orcontinuous manner. A solvent used in such a case is water; alcohols,such as methyl alcohol, ethyl alcohol, or isopropyl alcohol; aromatic oraliphatic hydrocarbons, such as benzene, toluene, xylene, cyclohexane,or n-hexane; ester compounds, such as ethyl acetate; ketone compounds,such as acetone or methyl ethyl ketone; and the like. It is preferableto use at least one kind selected from the group consisting of water andlower alcohols having 1 to 4 carbon atoms, from solubility of the rawmaterial monomer and the polycarboxylic acid for a cement dispersantobtained. Of those, it is further preferable to use water as a solventfrom the point that desolvent step can be omitted. In a case that maleicanhydride is used for copolymerization, polymerization using an organicsolvent is preferable.

In the case of conducting an aqueous solution polymerization,water-soluble polymerization initiators, such as persulfuric acid saltsof ammonia or alkali metals; hydrogen peroxide; azoamidine compounds,such as azobis-2-methylpropione amidine hydrochloride; and the like areused as the polymerization initiator. In this case, an accelerator, suchas sodium hydrogen sulfite or Mohr's salt can be used together.

Further, in the solution polymerization using lower alcohols, aromaticor aliphatic hydrocarbons, ester compounds, or ketone compounds as asolvent, peroxides, such as benzoyl peroxide or lauroyl peroxide;hydroperoxides, such as cumene hydroperoxide; azocompounds such asazobisisobutyronitrile; and the like are used as a polymerizationinitiator. In this case, an accelerator such as amine compounds can beused together. Furthermore, in the case of using water-lower alcoholmixed solvent, it is possible to use by appropriately selecting from theabove-mentioned various polymerization initiators or combination of thepolymerization initiators and accelerators.

The bulk polymerization is conducted within the temperature range of 50to 200° C. using peroxides, such as benzoyl peroxide or lauroylperoxide; hydroperoxides such as cumene hydroperoxide; azo compoundssuch as azobisisobutyronitrile; and the like as a polymerizationinitiator.

The polycarboxylic acid for a cement dispersant thus obtained is used asa main component of the cement dispersant as it is. If necessary, it maybe used by neutralizing a copolymer with an alkaline substance. Examplesof such an alkaline substance are preferably inorganic salts, such ashydroxides, chlorides and carbonates of monovalent metals and divalentmetals; ammonia; organic amines; and the like. In a case that maleicanhydride is used for copolymerization, the thus obtained copolymer maybe directly used as a cement dispersant or may be hydrolized and thenused.

The repeating unit of the polycarboxylic acid for a cement dispersant iswithin the range of, in weight ratio, (I)/(II)/(V)=1-99/99-1/0-50,preferably (I)/(II)/(V)=50-99/50-1/0-49, more preferably(I)/(II)/(V)=60-95/40-5/0-30, and most preferably(I)/(II)/(V)=70-95/30-5/0-10. Further, it is within the range of, inweight ratio, (III)/(IV)/(VI)=1-99/99-1/0-50, preferably (III)/(IV)/(VI)=50-99/50-1/0-49, more preferably (III)/(IV)/(VI)=60-95/40-5/0-30, andmost preferably (III)/(IV)/(VI)-70-95/30-5/0-10. Further, the weightaverage molecular weight of the polycarboxylic acid for a cementdispersant is 5,000 to 200,000, and preferably 10,000to 100,000. Ifthose component ratios and weight average molecular weight are fallenoutside the above ranges, a cement dispersant which exhibits high waterreducing performance and slump loss preventing performance cannot beobtained.

A cement used is not limited, but hydraulic cements, such as ordinaryportland cement, alumina cement and various mixed cements are general.

The polycarboxylic acid for a cement dispersant can be used alone or asmixtures thereof as a main component of the cement dispersant as it isor in the form of an aqueous solution, and may be used in combinationwith other known cement admixtures. Examples of such cement admixturesare conventional cement dispersants, air-entraining agents, cementwetting agents, expanding materials, water-proof agents, retardingagents, accelerating agents, water-soluble polymeric substances,thickeners, coagulating agents, dry shrinkage reducing agents, strengthincreasing agents, cure accelerating agents, defoaming agents, and thelike.

The cement composition of the present invention comprises at leastwater, a cement and a cement dispersant, wherein as the cementdispersant the cement composition comprises the polycarboxylic acid fora cement dispersant of the present invention. The polycarboxylic acidfor a cement dispersant is added in an amount of 0.01 to 1.0%, andpreferably 0.02 to 0.5%, of the cement weight in the cement composition.This addition brings about preferred various effects, such as reductionin unit water amount, increase in strength, or improvement indurability. If the amount used is less than 0.01%, it is insufficient inperformance, and conversely, even if it is used in an amount exceeding1.0%, the effect is not substantially increased, which isdisadvantageous from the economical standpoint.

Methods for producing the cement composition of the present inventionare not especially limited and there can be exemplified the same mannersas those for producing the conventional cement compositions, such as amethod that, when cement and water and other materials if necessary aremixed, the cement dispersant, its aqueous dispersion or aqueous solutionis added to and mixed with them; a method that cement and water andother materials if necessary are mixed, and then the cement dispersant,its aqueous dispersion or aqueous solution is added to and mixed withthe thus obtained mixture; a method that cement other materials ifnecessary are mixed, and then the cement dispersant, its aqueousdispersion or aqueous solution and water are added to and mixed with thethus obtained mixture; a method that cement and the cement dispersant,its aqueous dispersion or aqueous solution and other materials ifnecessary are mixed, and then water is added to and mixed with the thusobtained mixture.

In a case that the cement dispersant contains not only polycarboxylicacid-but also a dispersant other than poly)carboxylic acid,polycarboxylic acid and the other dispersant may be seperately added.

As embodiments of the cement composition, there can be exemplifiedcement water paste (cement water slurry), mortar or concrete. The cementwater paste contains a cement, water and a cement dispersant asessential components. The mortar contains the same components as thecement water paste and further contains as an essential component a fineaggregate such as sand. The concrete contains the same components as themortar and further contains as an essential component coarse aggregatesuch as cobble or crushed stone.

(Effects and Advantages of the Invention)

Using as a cement dispersant the polycarboxylic acid for a cementdispersant produced according to the production method of the presentinvention can achieve high water reduction of a cement composition suchas a concrete or a mortar.

DETAILED DESCRIPTION OF TEE PREFERRED EMBODIMENTS

The present invention is explained below in more detail by the examples,but the present invention is not limited thereto. In the examples,unless otherwise indicated, “%” means “% by weight”, and “part” means“part by weight” in the examples.

In the below-mentioned Examples 1-2 and Comparative Example 1, themolecular weight distribution were measured under the followingconditions:

[Measurement of Molecular Weight Distribution]

Apparatus GPC HLC-8020 produced by TOSOH K.K. Eluent Kind:tetrahydrofuran Flow rate: 1.0 (ml/min) Column Kind: Product of TOSOHK.K. TSKgel G40000HXL +G3000HXL +G3000HXL +G2000HXL 7.8 Ml I.D. X300 mlrespectively Calibration curve: Polystyrene standard molecular weight

In-Examples 4-6 and Comparative Examples 3-4, molecular weightdistribution was measured on a basis converted into that of polyethyleneglycol.

EXAMPLE 1

(Production of alkylene oxide adduct (1) of unsaturated alcohol typemonomer (polyalkylene glycol ether-based monomer (1)))

999 Parts of 3-methyl-3-butene-1-ol, and 5 parts of sodium hydride werecharged into a stainless steel high pressure reactor equipped with athermometer, a stirrer, and a nitrogen and oxygen introduction pipe.Inner atmosphere of the reactor was substituted with nitrogen understirring, and was heated to 140° C. under nitrogen atmosphere. Whilemaintaining 140° C. under safe pressure, 5,117 parts of ethylene oxidewere introduced into the reactor for 5 hours. Thereafter, thetemperature was maintained for 2 hours to complete alkylene oxideaddition reaction, thereby obtaining an unsaturated alcohol (hereinafterreferred to as “IPN-10”) in which 10 moles, on the average, of ethyleneoxide were added to 3-methyl-3-butene-1-ol. Subsequently, this reactorwas cooled to 50° C., and after taking out 3,198 parts of IPN-10, thereactor was heated to 140° C. under nitrogen atmosphere. Whilemaintaining 140° C. under a safe pressure, 6,302 parts of ethylene oxidewere introduced into the reactor for 8 hours. The temperature was thenmaintained for 2 hours to complete alkylene oxide addition reaction,thereby obtaining an unsaturated alcohol (hereinafter referred to as“IPN-35”) in which 35 moles, on the average, of ethylene oxide wereadded to 3-methyl-3-butene-1-ol. The area ratio of the shoulder-shapedpeak on the higher molecular weight side of the main peak was 4.70%. TheGPC chart is shown in FIG. 1.

EXAMPLE 2

(Production of alkylene oxide adduct (2) of unsaturated alcohol typemonomer (polyalkylene glycol ether-based monomer (2)))

999 Parts of 3-methyl-3-butene-1-ol, and 5 parts of sodium hydride werecharged into a stainless steel high pressure reactor equipped with athermometer, a stirrer, and a nitrogen and oxygen introduction pipe.Inner atmosphere of the reactor was substituted with nitrogen understirring, and was heated to 100° C. under nitrogen atmosphere. Whilemaintaining 100° C. under safe pressure, 5,117 parts of ethylene oxidewere introduced into the reactor for 8 hours. Thereafter, thetemperature was maintained for 2.5 hours to complete alkylene oxideaddition reaction, thereby obtaining an unsaturated alcohol (hereinafterreferred to as “IPN-10”) in which 10 moles, on the average, of ethyleneoxide were added to 3-methyl-3-butene-1-ol. Subsequently, this reactorwas cooled to 50° C., and after taking out 3,198 parts of IPN-10, thereactor was heated to 100° C. under nitrogen atmosphere. Whilemaintaining 100° C. under a safe pressure, 6,302 parts of ethylene oxidewere introduced into the reactor for 10 hours. The temperature was thenmaintained for 3 hours to complete alkylene oxide addition reaction,thereby obtaining an unsaturated alcohol (hereinafter referred to as“IPN-35”) in which 35 moles, on the average, of ethylene oxide wereadded to 3-methyl-3-butene-1-ol. The area ratio of the shoulder-shapedpeak on the higher molecular weight side of the main peak was 2.89%. TheGPC chart is shown in FIG. 2.

COMPARATIVE EXAMPLE 1

(Production of alkylene oxide adduct (1) of comparative unsaturatedalcohol type monomer (comparative polyalkylene glycol ether-basedmonomer (1)))

999 Parts of 3-methyl-3-butene-1-ol, and 5 parts of sodium hydride werecharged into a stainless steel high pressure reactor equipped with athermometer, a stirrer, and an oxygen introduction pipe. Inneratmosphere of the reaction was substituted with nitrogen under stirring,and was heated to 160° C. under nitrogen atmosphere, While maintaining160° C. under safe pressure, 5,117 parts of ethylene oxide wereintroduced into the reactor for 4 hours. Thereafter, the temperature wasmaintained for 1 hours to complete alkylene oxide addition reaction,thereby obtaining an unsaturated alcohol (hereinafter referred to as“IPN-10”) in which 10 moles, on the average, of ethylene oxide wereadded to 3-methyl-3-butene-1-ol. Subsequently, this reactor was cooledto 50° C., and after taking out 3,198 parts of IPN-10, the reactor washeated to 160° C. under nitrogen atmosphere. While maintaining 160° C.under a safe pressure, 6,302 parts of ethylene oxide were introducedinto the reactor for 6 hours. The temperature was then maintained for 1hours to complete alkylene oxide addition reaction, thereby obtaining anunsaturated alcohol (hereinafter referred to as “IPN-35”) in which 35moles, on the average, of ethylene oxide-were added to3-methyl-3-butene-1-ol. The area ratio of the shoulder-shaped peak onthe higher molecular weight side of the main peak was 11.86%. The GPCchart is shown in FIG. 3.

EXAMPLE 3

(Production of methacrylic ester (1) of polyalkylene glycol(polyalkylene glycol ester-based monomer (1)))

8.2 Parts of methanol, and 0.2 parts of sodium hydroxide were chargedinto a stainless steel high pressure reactor equipped with athermometer, a stirrer, and a nitrogen and oxygen introduction pipe.Inner atmosphere of the reactor was substituted with nitrogen understirring, and was heated to 120° C. under nitrogen atmosphere. Whilemaintaining 120° C. under safe pressure, 116.6 parts of ethylene oxidewere introduced into the reactor for 1 hour. Thereafter, the temperaturewas maintained for 1 hour to complete alkylene oxide addition reaction,thereby obtaining an alcohol in which 3 moles, on the average, ofethylene oxide were added to methanol. Subsequently, the reactor washeated to 155° C. and 855 parts of ethylene oxide were introduced intothe reactor for 3 hours under a safe pressure. The temperature was thenmaintained for 1 hours to complete alkylene oxide addition reaction,thereby obtaining methoxypolyethylene glycol (hereinafter referred to as“PGM-25”) in which 25 moles, on the average, of ethylene oxide wereadded to methanol.

Methacrylic ester of methoxypolyethylene glycol (methoxypolyethyleneglycol monomethacrylate) was obtained by esterification between thePGM-25 and methacrylic acid in a common manner.

COMPARATIVE EXAMPLE 2

(Production of comparative methacrylic ester (1) of polyalkyleneglycol(comparative polyalkylene glycol ester-based monomer (1)))

8.2 Parts of methanol, and 0.2 parts of sodium hydroxide were chargedinto a stainless steel high pressure reactor equipped with athermometer, a stirrer, and a nitrogen and oxygen introduction pipe.Inner atmosphere of the reactor was substituted with nitrogen understirring, and was heated to 120° C. under nitrogen atmosphere. Whilemaintaining 120° C. under safe pressure, 116.6 parts of ethylene oxidewere introduced into the reactor for 1 hour. Thereafter, the temperaturewas maintained for 1 hour to complete alkylene oxide addition reaction,thereby obtaining an alcohol in which 3 moles, on the average, ofethylene oxide were added to methanol. Subsequently, the reactor washeated to 170° C. and 855 parts of ethylene oxide were introduced intothe reactor for 3 hours under a safe pressure. The temperature was thenmaintained for 1 hours to complete alkylene oxide addition reaction,thereby obtaining methoxypolyethylene glycol (hereinafter referred to as“PGM-25”) in which 25 moles, on the average, of ethylene oxide wereadded to methanol.

Methacrylic ester of methoxypolyethylene glycol (methoxypolyethyleneglycol monomethacrylate) was obtained by esterification between thePGM-25 and methacrylic acid in a common manner.

EXAMPLE 4

(Production of polycarboxylic acid (1) for cement dispersant)

50 Parts of the unsaturated alcohol (hereinafter referred to as“IPN-35”) in which 35 moles, on the average, of ethylene oxide wereadded to 3-methyl-3-butene-1-ol, as produced in Example 1, 6.4 parts ofmaleic acid, and 24.2 parts of water were charged in a glass reactorequipped with a thermometer, a stirrer, a dropping funnel, a nitrogenintroduction pipe, and a reflux condenser, and the charged materialswere heated to 60° C. under stirring. 14.3 Parts of 6% ammoniumpersulfate aqueous solution were added dropwise for 3 hours. Thereafter,the temperature was maintained for 1 hour to complete copolymerizationreaction, and 30% NaOH aqueous solution was added dropwise to neutralizeup to pH of 7.0 to obtain a polycarboxylic acid (1) for a cementdispersant, comprising a copolymer aqueous solution having a weightaverage molecular weight of 33,400, of the present invention.

EXAMPLE 5

(Production of polycarboxylic acid (2) for cement dispersant)

50 Parts of the unsaturated alcohol (hereinafter referred to as“IPN-35”) in which 35 moles, on the average, of ethylene oxide wereadded to 3-methyl-3-butene-1-ol, as produced in Example 2, 6.4 parts ofmaleic acid, and 24.2 parts of water were charged in a glass reactorequipped with a thermometer, a stirrer, a dropping funnel, a nitrogenintroduction pipe, and a reflux condenser, and the charged materialswere heated to 60° C. under stirring. 14.3 Parts of 6% ammoniumpersulfate aqueous solution were added dropwise for 3 hours. Thereafter,the temperature was maintained for 1 hour to complete copolymerizationreaction, and 30% NaOH aqueous solution was added dropwise to neutralizeup to pH of 7.0 to obtain a polycarboxylic acid (2) for a cementdispersant, comprising a copolymer aqueous solution having a weightaverage molecular weight of 45,500, of the present invention.

COMPARATIVE EXAMPLE 3

(Production of comparative polycarboxylic acid (1) for cementdispersant)

50 Parts of the unsaturated alcohol (hereinafter referred to as“IPN-35”) in which 35 moles, on the average, of ethylene oxide wereadded to 3-methyl-3-butene-1-ol, as produced in Comparative Example 1,6.4 parts of maleic acid, and 24.2 parts of water were charged ina-glass reactor equipped with a thermometer, a stirrer, a droppingfunnel, a nitrogen introduction pipe, and a reflux condenser, and thecharged materials were heated to 60° C. under stirring. 14.3 Parts of 6%ammonium persulfate aqueous solution were added dropwise for 3 hours.Thereafter, the temperature was maintained for 1 hour to completecopolymerization reaction, and 30% NaOH aqueous solution was addeddropwise to neutralize up to pH of 7.0 to obtain a comparativepolycarboxylic acid (1) for a cement dispersant, comprising a copolymeraqueous solution having a weight average molecular weight of 15,300.

EXAMPLE 6

(Production of polycarboxylic acid (3) for cement dispersant) 120 Partsof water were charged into a glass reactor equipped with a thermometer,a stirrer, a dropping funnel, a nitrogen introduction pipe, and a refluxcondenser. Inner atmosphere of the reactor was substituted with nitrogenunder stirring, and was heated to 80° C. under nitrogen atmosphere.Monomer aqueous solution and 24 parts of 2.3% ammonium persulfateaqueous solution were added dropwise for 4 hours, wherein the monomeraqueous solution was a mixture of 50 parts of methoxypolyethylene glycolmonomethacrylate as produed in Example 3, 10 parts of methacrylic acid,0.5 parts of mercaptopropionic acid and 90 parts of water. After thedropping was finished, further, 6 parts of 2.3% ammonium persulfateaqueous solution were added dropwise for 1 hour. Thereafter,subsequently, the temperature 80° C. was maintained to completepolymerization reaction, thereby obtaining a polycarboxylic acid (3) fora cement dispersant, comprising a copolymer aqueous solution having aweight average molecular weight of 20,000, of the present invention.

COMPARATIVE EXAMPLE 4

(Production of comparative polycarboxylic acid (2) for cementdispersant)

120 Parts of water were charged into a glass reactor equipped with athermometer, a stirrer, a dropping funnel, a nitrogen introduction pipe,and a reflux condenser. Inner atmosphere of the reactor was substitutedwith nitrogen under stirring, and was heated to 80° C. under nitrogenatmosphere. Monomer aqueous solution and 24 parts of 2.3% ammoniumpersulfate aqueous solution were added dropwise for 4 hours, wherein themonomer aqueous solution was a mixture of 50 parts ofmethoxypolyethylene glycol monomethacrylate as produed in ComparativeExample 2, 10 parts of methacrylic acid, 0.5 parts of mercaptopropionicacid and 90 parts of water. After the dropping was finished, further, 6parts of 2.3% ammonium persulfate aqueous solution were added dropwisefor 1 hour. Thereafter, subsequently,the temperature 80° C. wasmaintained to complete polymerization reaction, thereby obtaining acomparative polycarboxylic acid (2) for a cement dispersant, comprisinga copolymer aqueous solution having a weight average molecular weight of20,000.

EXAMPLES 7 TO 9, AND COMPARATIVE EXAMPLES 5 TO 6

Mortar Test

Mortar test was conducted using the polycarboxylic acids (1), (2) and(3) for a cement dispersant of the present invention, and thecomparative polycarboxylic acids (1) and (2) for a cement.

Blending proportions of materials and mortar used in the test were 400 gof ordinary Portland cement (Chichibu-Onoda Cement Corporation), 800 gof standard sand (Tdyoura), and 260 g of water containing variouspolymers.

Mortar was prepared with mechanical kneading by a mortar mixer, andmortar was packed in a hollow cylinder having a diameter of 55 mm, andheight of 55 mm. Next, after lifting up the cylinder vertically, adiameter of mortar spread on a table was measured in two directions, andthe average was used as a flow value. The results are shown in Tables 1and 2.

TABLE 1 Rate of poly- Weight Addition Polycarboxylic merization (%)average amounts Flow acid for cement IPN-35 Maleic molecular (wt %)Value dispersant used a) acid weight b) (mm) Example 7 Polycarboxylic77.8 98.9 33400 0.11 95 acid (1) for cement dispersant Example 8Polycarboxylic 79.8 99.9 45500 0.11 97 acid (2) for cement dispersantComparative Comparative 56.7 72.0 15300 0.13 97 Example 5 polycaroxylicacid (1) for cement dispersant a) 35 Moles of EO (ethyleneoxide) wereadded to 3-methyl-3-butene-1-ol b) Weight % of solid content to cement

From Table 1, Rates of polymerization of maleic acid and IPN-35 are 72%and 56.7% in the comparative polycarboxylic acid for a cementdispersant, whereas those are very high as 98.9% and 77.8% in thepolycarboxylic acid (1) for a cement dispersant of the presentinvention, and 99.9% and 79.8% in the polycarboxylic acid (2) of acement dispersant of the present invention. Therefore, the cementdispersant of the present invention decreases its addition amount ascompared with the comparative cement dispersant, and can be highlypolymerized up to a molecular weight suitable as a cement dispersant. Asa result, it is apparent that water reducing property is improved.

TABLE 2 Weight Polycarboxylic average Addition Flow acid for cementmolecular amounts Value dispersant used weight (wt %) (mm) Example 9Polycarboxylic 20,000 0.13 109 acid (3) for cement dispersantComparative Comparative 20,000 0.13 103 Example 6 Polycarboxylic acid(2) for cement dispersant

From Table 2, it is understood that the cement dispersant (3) has ahigher mortar flow value and superior dispersibility as compared withthe comparative cement dispersant (2) at the same amount added (0.13%).Therefore, the cement dispersant of the present invention decreases itsaddition amount as compared with the comparative cement dispersant, andincreases water, reducing performance

What is claimed is:
 1. A cement composition comprising: a) at leastwater, a cement and a cement dispersant; b) wherein said cementdispersant comprises a polycarboxylic acid; c) wherein thepolycarboxylic acid is a copolymer obtained by copolymerizing comonomersincluding a polyalkylene glycol ether monomer and an unsaturatedcarboxylic acid monomer; d) wherein said polyalkylene glycol ethermonomer is obtained by reacting in the range of 80 to 155° C. analkylene oxide with an unsaturated alcohol represented by ROH; e)wherein said polyalkylene glycol ether monomer is represented byRO—(AO)_(n)—H, wherein R represents an organic group having anunsaturated bond, AO represents an oxyalkylene group, and n represents amolar number of addition of AO; f) wherein said polyalkylene glycolether monomer has a polyalkylene glycol ether chain as a side chain; g)wherein the end group of the polyalkylene glycol ether chain is ahydroxyl group; and h) wherein the weight average molecular weight ofthe polycarboxylic acid is 5,000 to 200,000.
 2. A cement compositioncomprising at least water, a cement and a cement dispersant, a) whereinsaid cement dispersant comprises a polycarboxylic acid having apolyalkylene glycol as a side chain, b) wherein the polycarboxylic acidincludes: a polyalkylene glycol monomer unit having the polyalkyleneglycol as a side chain and a carboxylic acid monomer unit; c) whereinthe polyalkylene glycol monomer unit includes a polyalkylene glycolether unit; d) wherein the end group of the polyalkylene glycol is ahydroxyl group; e) wherein a polyalkylene glycol monomer of thepolyalkylene glycol monomer unit is a polyalkylene glycol monomer havinga molecular weight distribution which has a main peak, but has no secondpeak on the higher molecular weight side of the main peak, or has asecond peak on the higher molecular weight side of the main peak in anarea ratio of 8% or less based on the total area of the main peak andthe second peak, wherein said molecular weight distribution is generatedwith a GPC apparatus calibrated with polystyrene and using atetrahydrofuran eluent having a flow rate of 1.0 ml/min; and f) whereinthe polyalkylene glycol is obtained by reacting alkylene oxide with anunsaturated alcohol.
 3. The cement composition of claim 1, wherein thepolycarboxylic acid includes the following repeating units: apolyalkylene glycol ether unit (I) represented by the general formula(1) below:

where: R¹ to R³ each independently represent hydrogen or methyl group;R⁵O represents one kind or a mixture of two or more kinds of oxyalklenegroup having 2 to 4 carbon atoms, in the case of two or more kinds,those may be added in a block state or random state; R⁶ representshydrogen; R⁴ represents —CH₂—, —(CH₂)₂— or —C(CH₃)₂—; and p representsan integer of 1 to 300; and a dicarboxylic acid unit (II) represented bythe general formula (2) below:

where: M¹ an M² each independently represent hydrogen, monovalent metal,divalent metal, ammonium or organic amine; X represents —OM² or—Y—(R⁷O)rR⁸; Y represents —O— or —NH—; R⁷O represents one kind or amixture of two or more kinds of oxyalkylene group having 2 to 4 carbonatoms, in the case of two or more kinds, those may be added in a blockstate or a random state; R⁸ represents hydrogen, alkyl group having 1 to22 carbon atoms, phenyl group, aminoalkyl group, alkylphenyl group, orhydroxyalky group (each alkyl group in the aminoalkyl, alkylphenyl andhydroxyalkyl groups having 1 to 22 carbon atoms); r is an integer of 0to 300; and an acid anhydride group (—CO—O—CO—) may be formed in placeof the —COOM¹ and COX groups between carbon atoms to which the —COOM¹and COX groups should be bonded respectively; wherein a polyalkyleneglycol ether monomer, which is obtained by addition reaction of alkyleneoxide having 2 to 4 carbon atoms in the range of 80 to 155° C. with anunsaturated alcohol (B-1) represented by the general formula (3) below:

where: R¹ to R³ each independently represent hydrogen or methyl group;and R⁴ represents —CH₂—, —(CH₂)₂—, or —C(CH₃)₂—, is the polyalkyleneglycol ether monomer giving the general formula (1) which is therepeating unit.
 4. The cement composition of claim 2, wherein thepolyalkylene glycol is obtained by reacting alkylene oxide in the rangeof 80 to 155° C. with an unsaturated alcohol represented by the generalformula (3)

where, R¹ to R³ each independently represent hydrogen or methyl group,and R⁴ represents —CH₂—, —(CH₂)₂—, or —C(CH₃)₂—).
 5. The cementcomposition of claim 2, wherein the polycarboxylic acid includes thefollowing repeating units: a polyalkylene glycol ether unit (I)represented by the general formula (1) below:

where: R¹ to R³ each independently represent hydrogen or methyl group;R⁵O represents one kind or a mixture of two or more kinds of oxyalkylenegroup having 2 to 4 carbon atoms, in the case of two or more kinds,those may be added in a block state or random state; R⁶ representshydrogen; R⁴ represents —CH₂—, —(CH₂)₂ or —C(CH₃)₂—; and p represents aninteger of 1 to 300; and a dicarboxylic acid unit (II) represented bythe general formula (2) below:

where: M¹ and M² each independently represent hydrogen, monovalentmetal, divalent metal, ammonium or organic amine; X represents —OM² or—Y—(R⁷O)rR⁸; Y represents —O— or —NH—; R⁷O represents one kind or amixture of two or more kinds of oxyalkylene group having 2 to 4 carbonatoms, in the case of two or more kinds, those may be added in a blockstate or a random state; R⁸ represents hydrogen, alkyl group having 1 to22 carbon atoms, phenyl group, aminoalkyl group, alkylphenyl group, orhydroxyalky group (each alkyl group in the aminoalkyl, alkylphenyl andhydroxyalkyl groups having 1 to 22 carbon atoms); r is an integer of 0to 300; and an acid anhydride group (—CO—O—CO—) may be formed in placeof the —COOM¹ and COX groups between carbon atoms to which the —COOM¹and COX groups should be bonded respectively; wherein a polyalkyleneglycol ether monomer, which is obtained by addition reaction of alkyleneoxide having 2 to 4 carbon atoms in the range of 80 to 155° C. with anunsaturated alcohol (B-1) represented by the general formula (3) below:

where: R¹ to R³ each independently represent hydrogen or methyl group;and R⁴ represents —CH₂—, —(CH₂)₂—, or —C(CH₃)₂—, is the polyalkyleneglycol ether monomer giving the general formula (1) which is therepeating unit.
 6. A cement composition comprising at least water, acement and a cement dispersant, a) wherein said cement dispersantcomprises a polycarboxylic acid having a polyalkylene glycol as a sidechain, b) wherein the polycarboxylic acid includes: a polyalkyleneglycol monomer unit having the polyalkylene glycol as a side chain and acarboxylic acid monomer unit; c) wherein the polyalkylene glycol monomerunit includes a polyalkylene glycol ether unit; d) wherein the end groupof the polyalkylene glycol is a hydroxyl group; e) wherein apolyalkylene glycol monomer of the polyalkylene glycol monomer unit is apolyalkylene glycol monomer having a molecular weight distribution whichhas a main peak, but has no second peak on the higher molecular weightside of the main peak, or has a second peak on the higher molecularweight side of the main peak in an area ratio of 8% or less based on thetotal area of the main peak and the second peak wherein said molecularweight distribution is generated with a GPC apparatus calibrated withpolystyrene and using a tetrahydrofuran eluent having a flow rate of 1.0ml/min; f) wherein the polyalkylene glycol is obtained by reactingalkylene oxide with an unsaturated alcohol; and g) wherein the alkyleneoxide is added to an active hydrogen-containing compound by an additionreaction in the presence of a base catalyst.
 7. A cement compositioncomprising at least water, a cement and a cement dispersant, a) whereinsaid cement dispersant comprises a polycarboxylic acid having apolyalkylene glycol as a side chain, b) wherein the polycarboxylic acidincludes: a polyalkylene glycol monomer unit having the polyalkyleneglycol as a side chain and a carboxylic acid monomer unit; c) whereinthe polyalkylene glycol monomer unit includes a polyalkylene glycolether unit, with the polyalkylene glycol ether unit being obtained byaddition reaction of alkylene oxide in the presence of a base catalyst;d) wherein the end group of the polyalkylene glycol is a hydroxyl group;e) wherein a polyalkylene glycol monomer of the polyalkylene glycolmonomer unit is a polyalkylene glycol monomer having a molecular weightdistribution which has a main peak, but has no second peak on the highermolecular weight side of the main peak, or has a second peak on thehigher molecular weight side of the main peak in an area ratio of 8% orless based on the total area of the main peak and the second peak,wherein said molecular weight distribution is generated with a GPCapparatus calibrated with polystyrene and using a tetrahydrofuran eluenthaving a flow rate of 1.0 ml/min; and f) wherein the polyalkylene glycolis obtained by reacting alkylene oxide with an unsaturated alcohol. 8.The cement composition according to claim 1, wherein said alkylene oxidehas 2 to 4 carbon atoms and wherein said unsaturated alcohol isrepresented by the general formula (3)

where: R¹ to R³ each independently represent hydrogen or methyl group:and R⁴ represents —CH₂—, —(CH₂)₂—, or —C(CH₃)₂—.
 9. The cementcomposition according to claim 1, wherein said unsaturated carboxylicacid monomer is represented by the general formula (2-2):

where: M¹ and M² each independently represent hydrogen, monovalentmetal, divalent metal, ammonium or organic amine; X represents —OM² or—Y—(R⁷O)rR⁸; Y represents —O— or —NH—; R⁷O represents one kind or amixture of two or more kinds of oxyalkylene group having 2 to 4 carbonatoms, in the case of two or more kinds, those may be added in a blockstate or a random state; R⁸ represents hydrogen, alkyl group having 1 to22 carbon atoms, phenyl group, aminoalkyl group, alkylphenyl group, orhydroxyalky group (each alkyl group in the aminoalkyl, alkylphenyl andhydroxyalkyl groups having 1 to 22 carbon atoms); r is an integer of 0to 300; and an acid anhydride group (—CO—O—CO—) may be formed in placeof the —COOM¹ and COX groups between carbon atoms to which the —COOM¹and COX groups should be bonded respectively.
 10. The cement compositionaccording to claim 1, wherein: a) said alkylene oxide has 2 to 4 carbonatoms; b) said unsaturated alcohol is represented by the general formula(3)

where: R¹ to R³ each independently represent hydrogen or methyl group:and R⁴ represents —CH₂—, —(CH₂)₂—, or —C(CH₃)₂—; and c) said unsaturatedcarboxylic acid monomer is represented by the general formula (2-2):

where: M¹ and M² each independently represent hydrogen, monovalentmetal, divalent metal, ammonium or organic amine; X represents —OM² or—Y—(R⁷O)rR⁸; Y represents —O— or —NH—; R⁷ represents one kind or amixture of two or more kinds of oxyalkylene group having 2 to 4 carbonatoms, in the case of two or more kinds, those may be added in a blockstate or a random state; R⁸ represents hydrogen, alkyl group having 1 to22 carbon atoms, phenyl group, aminoalkyl group, alkylphenyl group, orhydroxyalky group (each alkyl group in the aminoalkyl, alkylphenyl andhydroxyalkyl groups having 1 to 22 carbon atoms); r is an integer of 0to 300; and an acid anhydride group (—CO—O—CO—) may be formed in placeof the —COOM¹ and COX groups between carbon atoms to which the —COOM¹and COX groups should be bonded respectively.